It is generally known that high-voltage transformers, for example in a voltage range of from 110 kV or 380 kV and in a power range of 100 MVA or higher, both for inspection purposes and after termination of any possible maintenance or repair work or else directly after their fabrication, need to be tested intensively in order to ensure their correct functioning for the next operation time period, which is often a number of years. Both stationary and mobile testing stations are used. The latter are in particular constructed for in-situ testing of transformers, then dismantled and transported to the next use location. Even when the transport and construction of a mobile testing station is usually associated with a very high degree of complexity, this complexity is usually nevertheless lower than the complexity involved in transporting a transformer with a weight of, for example, 200 tons (t) to a stationary testing station. In addition, the downtime of a transformer undergoing testing is then significantly reduced.
In this case, both DC and AC testing stations are used, with which the corresponding test conditions can be produced. In particular, AC testing stations need to be capable of providing a high electrical testing power with variable frequency and variable voltage over a relatively long time period, often lasting several hours, for example, for a continuous load test or a short-circuit test. In addition to power electronics components such as inverters and rectifiers, for example, a test transformer is also required in order to convert, for example, the AC voltage generated by the converters to a voltage level required for the testing or else in order to match the voltage of the feed available to the inverters.
Such a transformer is a component with a considerable size and a considerable weight, for example 15t, owing to the high maximum test power required, for example 20 MVA or higher. The transport of such a transformer is disadvantageously performed in the form of special transport, for example on a flatbed truck, and is therefore particularly time-intensive and complex. The construction, installation and first operation of such a test transformer in situ is also associated with a considerable amount of outlay in terms of time and logistics.